Multi-Dimensional Fragility of Structures: Formulation and Evaluation Technical rept

摘要

A multi-dimensional definition of fragility is developed considering multiple parameters, including structural response variables such as floor accelerations and interstory drifts. Limit states are defined based on these multiple variables, considered as random variables in the calculation of fragility. A probabilistic description of the limit state has been adopted to calculate fragility. A generalized formula for multidimensional threshold limit states is proposed, and various cases are considered to illustrate the formulation. The MCEER west coast Demonstration Hospital located in the San Fernando Valley in Southern California was considered to show the applicability of this technique. The development of fragility for different cases shows the importance of correct evaluation of the limit states for comparison of different techniques. The MCEER generated ground motion series, as well as those developed for the well-known SAC (SEAOC-ATC-CUREE) project are used as input for the illustration and comparison of fragility calculations. The study investigates the sensitivity of fragility curves when uncertainties in limit states, usually defined from consensus of engineering and functionality criteria, are considered. Influence of structural and response parameters, such as stiffness, acceleration and displacement thresholds, input ground motion, and uncertainties due to structural modeling, are investigated. Different structural parameters that drastically affect the fragility are also considered, such as damping, that reduce structural response (deformations in particular).